Because Earth orbits around the sun, causing the position to seemingly change as the Earth moves. Orion can't be seen in summer because it appears when the sun is out. The reason it doesn't appear at night is because the earth is titled differently on it's axis then in, say winter.
I hope this helps you out.
Explanation:
Given that,
The disintegration constant of the nuclide,
(a) The half life of this nuclide is given by :
(b) The decay equation of any radioactive nuclide is given by :
Number of remaining sample in 4.44 half lives is :
So,
(c) Number of remaining sample in 14.6 days is :
So,
Hence, this is the required solution.
The electron won't be traveling because it is as u say "fixed in place".